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Study On Preparation And Modification Of LiNi0.5Mn1.5O4and LiNi1/3Co1/3Mn1/3O2Cathode Materials For Lithium Ion Battery

Posted on:2013-07-18Degree:DoctorType:Dissertation
Country:ChinaCandidate:O ShaFull Text:PDF
GTID:1261330392969764Subject:Applied Chemistry
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The preparation and modification of spinel high-voltage cathode materialLiNi0.5Mn1.5O4and layered cathode material LiNi1/3Co1/3Mn1/3O2weresystematacially studied in this paper. The electrochemical properties ofLiNi0.5Mn1.5O4/Li4Ti5O12and LiNi1/3Co1/3Mn1/3O2/Li4Ti5O12full cells were alsodiscussed preliminarily.With NiCO3·2Ni(OH)2·4H2O as Ni source, LiNi0.5Mn1.5O4cathode materialsynthesized by ball-milling solid state method under the optimal process conditions(800℃,20h), could reach a discharge capacity of105.6mAh·g-1at the rate of1Cwith the capacity retention of89.7%after100cycles.The effect of low-temperature annealing treatment on the structure andelectrochemical performance of spinel LiNi0.5Mn1.5O4cathode material was studiedby the optimized sol-gel method. The results showed that the content of Mn3+in theproduct was decreased and highly purity product was obtained after annealingtreatment. The annealed material with good electrochemical performance could reacha discharge capacity of125.0mAh·g-1at the rate of1C with the capacity retention of97.6%after100cycles.The Cu2+doped LiNi0.45Cu0.05Mn1.5O4cathode material had been preparedsuccessfully. It was found that doping with Cu2+could reduce the electrodepolarization and ameliorate the cycle performance of the spinel at high rate and hightemperature. The LiNi0.45Cu0.05Mn1.5O4cathode material could reserve95.7%of theinitial discharge capacity (114.2mAh·g-1) after150cycles at the discharge rate of20C, and could deliver127.3mAh·g-1at high temperature (55℃) and5C with acapacity fading rate of2.0%after100cycles.Multiple ion doped LiNi0.475Al0.01Cr0.04Mn1.475O3.95F0.05cathode material wasfirstly reported, which could achieve136.6,134.0,129.0,119.9,104.5and86.4mAh·g-1at0.2C,1C,5C,10C,15C and20C, respectively. In addition, whencycled at55℃for100cycles, the capacity fading rates were only0.3%and4.4%at1C and10C, respectively. After multiple ion doping, the electrochemical reaction activity and cycle reversibility of the material had been improved, promoting theenhancement of its charge-discharge performance at high current.A cheap and nontoxic urea-based sol-gel method for the synthesis ofLiNi0.5Mn1.5O4cathode material was proposed for the first time. The obtainedmaterial could achive132.1,123.3and113.0mAh·g-1at1C,3C and5C,respectively. In addition, in the research of the electrochemical performance ofLiNi0.5Mn1.5O4/Li4Ti5O12full cell, the cell designed by some excess positive capacityshowed preferable cycle life and reversibility, which could achive98.7mAh·g-1after200cycles at0.5C and the coulombic efficiencies were around99%.Layered LiNi1/3Co1/3Mn1/3O2cathode material was synthesized by hightermperature solid state method with LiOH·H2O and Ni1/3Co1/3Mn1/3(OH)2as rawmaterials. The full cell (LiNi1/3Co1/3Mn1/3O2/Li4Ti5O12) matched with Li4Ti5O12anodematerial could reach the discharge capacity of147.3,139.2,119.6and86.0mAh·g-1at0.2C,1C,5C and10C, respectively. Besides, it also could reserve83.7%after1000cycles at the rate of5C, revealing excellent charge-discharge performance andcycle life at high current.
Keywords/Search Tags:Lithium ion battery, Cathode materials, Spinel LiNi0.5Mn1.5O4, Modification, Urea, Layered LiNi1/3Co1/3Mn1/3O2, Full cell
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